Improved double volute spbilg



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LetzersPatent No. 80,628, dated August 4,1868.

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Be it known that I, JOSEPH HOBA'RT, 'of' Boston, in the county of Sufolk, and State of Massachusetts, have invented a new andi'usel'ul Improvement in Double V'oluteiSprings;v 'andI do hereby'declare that the following is a full, clear, and Yexact'description.of the construction of"Y the same, reference being had to the annexeddrawings, making apart of this specification, in which- Figure lH is a view of a flat, straight har, rolled and cut to the proper dimensions for forming a Spring. l

Figure 2 is a view of thesame har, doubled together in'preparationgfor'ceiling. Figure 3 is a view of the completed spring, with the double end in the centre. Figure 4 is a View ofthe completed spring, as sometimes coiled, with the double end 'on the outside. Figures 5 and 6 represent Variations `in theV form ofthe bar prepared-for coiling, i A double `volute spring, composed of a Single bar, was patented by D. G. Rollin,rFebruary 23, 1858, and `reissued, October 15, 1867, to the present applicant.

A mode of forming such a spring has been patented by Freeland t Ward, in which a wide bar is split and spread at one end, preparatory to ceiling. i

My improvementdifi'ers mainly from these, nswell as from'all others known to me,in bending and doub-y ling the bar to the required angle, in the plane of the spring, whereby Isecure increased strength andelasticit-y and durability, as well as economy of metal. i

In the drawings, hg. 2 represents a bar of ,meta-l, of the requisite breadth and thickness, in the .same condition as when received from the steciworks,bent to the required angle in the planeotthe spring.

ftake a fiat strip o` metal, of the requisite sine,- and heat it-as near the centre as practicable, and then, 'placing oir holdingvthe two ends so that they preserve the same plane, Ir bend the bar 4at its centre over any fixed rod or bar or resting-bed, upon which theedge of the metal rests, until the two ends ofthe `strip approach eachother enougdto cause something of a crimp at the point of bending. i

'I then hainmer down the bight or bend to flatten it, and the eilect of this is' not only to refine the metal,

i but to preserve the original fibre or: texture, to 4keep the s'velvedge oredge intact, and to render the liietal more compact and tough at that portion where strength ,is required.

The bar is then heated anew, and further bent and hammered as before, until the whole is brought to the' form-and conditioh required; cvery'sueii bending and hammering serving to increasestill further the strength and quality of the metal at itsbend.

The natural effect of thus bending the metal edgeways yover a rod is to'round that part where the two arms meet, and to cause the two inner edges, in proximity thereto, slightly-to` approach each other for efshort distance beforeithey commence to diver-gegend outof' this special feature alsd results another advantage hereinafter stated. K

The bar being mudo and coiled in proper'shape for-use, it is to be submitted to a hardening-bath., v By reason of the closeproximity of the oint where the arms meet to Vthe end of the bar, andot, theopen` ness of the space at that point, the oilof the bath has freenocess to ,the inner edges, and 'there is nothingy to 'offer any obstruction to their becoming properly tempered,` as well asall other parts of the springr,

Growing out of -thc above construction are the following additional advantages: VWhen the coiled spring` is in use, and under the pressure of an imposed weight, as the two free. ends approach each other, the two Varms corne in contact vwith each other at a short distance fromY their junction,

leaving a free space between this point of contact and the junction.`

YI sometimescurve/thc two arms of the spring gradually away fromeach other,'makingthe angle gradually increase from the point ofjuneture for a greater or less distance.

Now, when the `pressure is increased, this point of contact' shifts outwards, towards the free ends, and ,thus

is constantly changing as the pressure or weightis varied and hence the point of leverage, when the pressureis gradually increased, is steadily shifted forward from the bend, and the danger of breaking is lessened, at the same time that the stiffnessis increased `bythe angles being Vkept greater than they would'be if the point of bearing remained stationary.

In this last-namedl curved form oi' arm, I may also have the above-described feature ofthe approach of theA 'arms towards each other near their bight or bend; and, from these two features combined, I secure a further increase ofstrength and elasticity, resulting' from the fact that that portion of the spring lying back of the point where,'for the time being, the two arms of the springtouch each other, operates, by reason of the open space, as a reversed spring against the leverage of the pressure. l

Another form which I have used is represented in fig. 5, in which-there is a doublevc'urve in the angle of the spring. l j f v From this construction I attain the following result, viz, that the spring, under any pressure to which kit will be subjected, cannever be 'entirelyl closed, but, under the heaviest pressure that it can bear, will always retain a certain degree of elasticity, even when both ends of the spring come to a dead-bearing.

Still another modification is represented in fig. 6, in which the two free ends of the spring are brought n'ear together in the manufacture, leaving an opening somewhat elliptical in form. v l The result obtained from thi,` form yof construction is that the spring is easy and free under a light weight, but, under a heavy weight, both ends come to a bearing, and the power and strength of the spring are then, when mostA needed, greatly increased.- l

It may be more convenient, in the manufacture of my improved spring, to bend a square or round bar instead of a fiat one,'and afterwards roll it to the required thickness or iiatness for alspring, thus arrivi-ng at the same result; the leading characteristic in leach case, however, being that the hat bent-spring is dubled in the plane of the piece of metal, and not in a direction at right angles thereto, and that the two arms are not 'formed by cutting or slitting the metal. I

It'wll be evident, therefore, that .the fibre or grain and the metal are preserved intact, and not destroyed or weakened by slitting; that the edges or selvedges of the vbar or spring,- which are usually the hardest and toughest parts as compared with the centre portion, retain their hardness; that I avoid the making of sharp,l cntting,li`ragmentary, or bent-over or curled edges, which are incident to cutting the strip with a shears, and

'whichrequire afterwards to be hammered'or tiled, 0r otherwise to bey treated, in order to be again brought to v a smooth and even condition.

I also avoid the very considerable expense of shears for this slitting, or dies for stamping out or slitting the blank, as none are required. l I

What I claim as my invention, and desire to securebyietters Patent, i s l 1. A double volute spring, composed of a single bar of metal, and made by bending said bar at the` middle, doubling it upon itself, and ceiling the same around a mandrel, or otherwise, substantially as described.

2. Inmahing double volute springs, in the mannerset forth in the foregoing clause, I claim so lbending the .limbs that the edges thereof` shall describe lines of 'unequal curvature, but so that the curvature, commencing at or near the point of junction oi' said limbsshall increase fromthence outward towards the extremitiesthereof, substantially as described.

l3. In'making a double volute spring, in the manner set forth in therst clause, 'I claim bringing the two free ends near together, leaving an opening between the limbs, which narrows towards the ends, substantially as described. v l Y JOSEPH HOBART. Witnesses: I

BENJN. WORCESTER. 

